In a medium saucepan over medium high heat, bring brown rice and chicken stock to a boil and let simmer until the rice has absorbed the liquid and is tender, about 35 to 45 minutes. Fluff with a fork and set aside to cool.
Heat one tablespoon of olive oil in a skillet over medium high heat and cook garlic until fragrant. Add broccoli florets and brussels sprouts, and cook until the vegetables are tender. Season with salt and pepper to taste.
In small bowl, whisk together remaining olive oil, balsamic vinegar, lemon zest, and salt and pepper to taste.
Combine rice, broccoli, brussels sprouts, parsley, cranberries, pumpkin seeds, and dressing in a large bowl and mix until the ingredients are well coated. Serve warm or at room temperature.